Going by your logic, there will NEVER be a GOAT, only a current great fighter because your basis seems to be that as soon as someone loses, all their past accomplishments are null and void.
Everyone loses. Everyone will lose. It's the nature of the beast. There isn't a single prizefighter who will retire undefeated.
When you gain the ability to comprehend accomplishments based on when and how they happened, instead of how they ended, you will be able to understand things completely.
Eventually Anderson is going to lose, and when he does, there will be a slew of fans such as yourself who will claim he was never that good to begin with and will hop onto the bandwagon of whoever is the current great fighter. Right there is the problem with MMA fans.